The Parkinson's Institute has participated as one of the clinical centers in the NET-PD program during the last two funding periods. The current LS-1 trial underway is part of a multi-center, double-blind, study to determine if creatine is more effective than placebo in slowing the clinical decline in Parkinson's disease (PD) patients with early, treated PD. The Parkinson's Institute has enrolled 41 subjects into LS-1 trial and 30 subjects are still completing follow-up visits. The primary outcome will be a global measure incorporating multiple dimensions of disability due to PD. The hypothesis is that creatine 10 grams daily will be associated with less disease progression after 5 years, when compared to placebo. Secondary hypotheses are that the creatine-treated group will have greater efficacy and similar safety and tolerability to placebo. The specific aims of the Parkinson's Institute will be (1) to continue follow-up of all active patients according to the study protocol, using good clinical practices, (2) to focus on retention of all subjects, being mindful of changing needs of patients and caregivers as the study progresses and (3) to provide high quality clinical data in a timely manner. These aims are essential to the accurate and efficient analysis of study data, testing the study hypotheses. The long track record of excellence in clinical research at the Parkinson's Institute will be the foundation of our effort. Successful completion of the LSI will address a critical gap in the treatment of Parkinson's disease, since no intervention has unequivocally been proven to slow progression of PD. As the burden of disease increases worldwide, this becomes a critical public health concern.